Electric brake



-No. 606,9l7 Patented July 5, I898.

H. P. DAVIS.

ELECTRIC BRAKE.

(Application filed Oct. 22, 1891) 2 Sheets-Sheet I.

(No Model.)

/A/ VENTOP A TTOHNE y.

No. 606,9I7.

Y Patented July 5, I898. H. P. DAVIS. ELECTRIC BRAKE.

(Application film 1 Oct. 22, 1897.)

2 Sheets-Sheet 2.

(No Model.)

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' name STATES .A'rnNr Prion.

HARRY P. DAVIS,'OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO THE WESTINGHOUSEELECTRIC AND MANUFACTURING COMPANY, OF

PENNSYLVANIA.

ELECTRIC BRAKE.

SPECIFICATION forming part of Letters Patent No. 606,917,'dated.July 5,1898.

Application filed October 22, 1897. Serial No. 656,023. (No model.)

To all whom it may concern.-

Be it known that I, HARRY P. DAVIS, a citizen of the United States,residing in Pittsburg, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement in ElectricBrakes, (Case No. 756,) of which the following is a specification.

My invention relates to mechanism for controlling the operation ofelectrically-propelled vehicles, and particularly toelectrically-operated braking mechanism for such vehicles.

The object of my invention is to provide means whereby apparatus of thecharacter specified may be controlled more readily and operated moreeffectively than has been possi ble with apparatus which has heretoforebeen generally employed for this purpose.

I have found in practice that under certain conditions of operationas,for. example, when the rails are wet or coated with mud, ice, or snowand current is applied to brakemagnets connected in series with aplurality of motors acting as generators-one of the brake-shoes isliable'to stick, and thus completely stop the revolution of thecorresponding truck-wheels. If the controller is thrown to the emergencybraking position, this liability is particularly great. While thiscondition will stop the supply of current from the armature geared tothe wheels that have ceased to revolve, the other armature will furnishcurrent to both brake-magnets, and thus serve to prevent any rotation ofthe sliding wheels. It will be readily seen that under such conditionsno control whatever can be had over the sliding wheels eitherelectrically or by means of a hand-brake. I propose to obviate thisdifficulty by placing a brake-magnet in each armature-circuit. Then ifone pair of wheels is prevented from revolving by reason of excessivefriction of the corresponding brake and lack of friction between thewheels and the rails the corresponding armature will not only cease tosupply current to its brake-magnet, but the armature of the other motorwill supply current to said magnet which will be opposite indirection tothe magnetizing-current normally supplied to it. The brake-shoe willthus be demagnetized and the wheels released. The re leased wheels willthen begin to revolve and causethe corresponding armature to supplymagnetizing-current to its brake-magnet. If the brake should againstick, this operation would be repeated and the car be thus keptunderperfect control. lprovidealso an automatic demagnetizing switchwhich serves to throw the brake-magnets into circuit when thepower-current is shut off and to cut them out of circuit when thepower-current is again supplied to the motors.

In the accompanyingdrawings, Figure 1 is a diagram of anelectrically-propelled car equipment containing my invention. Fig. 2 isa side elevation of the deniagnetizihg-switch forming a part of theequipment shown in Fig. 1, the inclosin g casin g or boX of the switchbeing in section. Fig. 3 is a plan View of the demagnetizing-switch andits box, the cover of the latter being removed. Fig. 4. is a diagram ofthe circuits corresponding to the various positions of thecontroller-drum.

Referring particularly to Figs. 1, 2, and 3, the surface of thecontroller-drum is shown as developed into a plane, the workingpositions on the same being indicated by the spaces between the brokenlines. The spaces designated by numerals l to 13 are the operativepositions on the power side of the. controller-drum, and the spacesdesignated by the letters A, B, C, D, E, and Fare the operativepositions on the brake side of such drum. The contact-fingers G, C, C, 0E, R R R R R and T, which will be hereinafter designated as the mainstationary contact-fingers. cooperate, respectively, with thecontact-strips m to 00 on the drum in horizontal alinement therewith.The contact-fingers C and R also respectively engage and cooperate withthe strips 00 and 00 00 on the drum and will hereinafter be designatedas auxiliary stationary contacts. Permanent electrical connections areprovided between certain of the drum contact-strips, as is usual indevices of this character, these connections being clearly indicated inthe drawings.

It will be readily seen that the relative positions of the main andauxiliary contact-fingers are such that when the former are in position1 on the drum the latter will be in position 9 and that when the formerare in position A the latter will be in position 5, there being a vacantspace on the drum between positions 1 and A substantially equal in widthto three of the spaces designated by the reference letters and numerals.If this relation be borne in mind, the circuits corresponding to thevarious positions of the drum may be traced without difficulty.

A set of supplemental stationary contactfingers L (individuallydesignated as Z to Z and two sets of movable contacts P and B(respectively designated individually as p to p and b to 6 are alsoemployed for the purpose of securing the desired relation of motors andcooperating apparatus. The c011- tacts P and B are preferably in theform of strips and mounted upon a drum, which is either rigidly attachedto the shaft of the main drum or is geared thereto in any usual andwell-known manner, so that the contactfingers L and the strips P will bein engagement when the main drum is in position to supply line-currentto the motors and so that the contact-fingers L and the strips B will bein engagement when the main drum is in any one of the braking positions.The contactstrips of each set are permanently connected electrically, asis indicated in the drawings. The resistance R for the circuits isrendered variable by dividing it into five parts or sections '1', 1', rr and r as is usual in equipments of this general character. A blow-outmagnet K may also be employed, if desired. The two motor field-magnetsforming parts of the equipment are designated as F and F and thecorresponding motorarm atures as A and A M and M are the brake-magnets,which are respectively in circuit with the armatures A and A hen thecontrolling-drums are in any one of the braking positions, a localcircuit is established which contains two parallel branches, each ofwhich contains a motor and a corresponding brake-magnet. Anequalizing-wire connects the branches between the field-magnets and thearmatures, and the connections between corresponding ends of thebranches also have equalizing functions.

In order to demagnetize the brake-magnets when no braking effect isdesired, I provide an automatic switch, inclosed in a box M, theconstruction of which is as follows: m is an electromagnet, one terminalof the coil of which leads to the trolley or otherwise connects with thesource of current employed for actuating the motors by means of aconduct-or O, the other terminal of the coil being connected with theconductor 0, leading to the blow-out magnet K, and the latter beingconnected to the contact T by a conductor 0 Pivotally mountedlongitudinally in the box M is a-bar II, which has fastened to its underside a transversely-extending bar or plate H. One end of the bar II isprovided with an armature a, which is directly over the magnet 072, andthe other end of said bar is connected to the bottom of the box M bymeans of a coiled spring 3, which serves to hold the armature to out ofcontact with the poles of the magnet 07?. when the latter is notenergized. The bar II is provided at one end with a contact plate orstrip i, which extends transversely in both directions, and at itsopposite end with a similar plate or strip 11. The end of the box Mcorresponding to the strip 2' is provided with terminals 25 t i", theterminal i being permanently connected to the contact-strip i and theterminals 2? i" projecting inside the box in such position as to beengaged by the corresponding ends of the strip 11. The other end of thebox is provided with similar terminals I, F, and 25 which arecorrespondingly related to the strip 1'.

The relation of the circuits and the operation of the apparatus are asfollows, reference being had to Fig. 4 of the drawings in connectionwith the preceding figures: Assuming that the controller-drum is rotatedto bring the main stationary contacts into position 1 and the contacts Pinto engagement with the contacts L, the magnetm of thedemagnetizing-switch will attract itsarmature a, and thus rock the barII to separate the strips 2' and z" from the terminals '6 and t andbring them into engagement with the terminals 15 and The circuits of thebrake-magnets M and M will thus be broken and the conductors d and dinserted in lieu thereof. In this position the two motors will be inseries with all of the resistance Rin circuit, the path traversed by thecurrent being as follows: through conductor 0, magnet-coil m, conductorsO and 0 contact-finger T, contact-strips 0c and 2139, contact-finger Rresistance-sections r, r, r 0- and r conductors O and O contact-fingerZ, contact-strips 19 p finger Z field-magnet winding F, finger Z strips19 and 1)", finger Z armature A, switch-terminal t, plate 2', terminal iconductor (Z, conductor O ,'finger C, conductor 0 finger C strips 00 and00 finger O, conductor 0 finger Z field-magnet winding F finger Z stripsfiand 19", finger Z armature A switch-terminals t, plate 2'', terminal iconductor cl, and finger Gr to ground. It will be readily seen withouttracing the circuits in detail that when the main drum is turned tobring the main contact-fingers into position 2 the sections 1' and r ofthe resistance K are shortcircuited, the other portions of theresistance and the motors remaining in series. I11 position 3 theresistance-sections r, r, and r are short-circuited, leaving theremaining resistance-sections and the two motors in series. In positioni all of the sections of the resistance except 0- are short-circuitedand that section and the two motors are in series. In position 5 all ofthe resistance is cut out or sh'ort-circnited, leaving the two motors inseries without resistance. In position 6 the resistance-section r isreinserted. In position 7 resistance-sections r r and r are inserted andmotor A F is cut out. Position 8 is the same as position 7. In position9 resistance-sections r and r are cut out, the two motors beingconnected in parallel with the remaining portion of the resistance incircuit, the path traversed by the current being as follows: throughconductor O, magnet-coil m, conductors O and O finger T, strips and 00finger R resistance-sections r 0' and r finger R and conductor O tofinger From finger C one path is through strips 00 and 00 finger c,conductor 0 finger Z field-magnet winding F finger Z strips 19 and pfinger Z, armature A switch-terminal if, plate 1', terminal 25 andconductor d to ground contact-finger G, and the other path is throughconductor 0 finger Z, strips p and p finger Z fieldmagnet winding F,finger Z strips 19 and p finger Z armature A, switch-terminal 25, platet, and terminal i conductors cl and O finger 0, strips 00 and 00 toground contact-finger G. Position 10 is the same as position 9. Position11 differs only in the short-circuit ing of the additional section r ofthe resistance. In position 12 all of the resistance except the portion1' is short-circuited, and in position 13 the motors are in parallelwith all of the resistance cut out or short-circuited, this being thefinal running position on the power side.

In order to stop the car, the controller-drum is reversed until the mainstationary contactfingers are in position A and the contact-fingers Bare in engagement with contact-strips L. As soon as stationarycontact-finger T leaves position 1 in the reverse movement of the drumthe magnet m of the demagnetizin g-switch will be denergized and thespring 3 will throw the strips 1' and 71 into contact with terminals 15and 29, so that when position A is reached the brake-magnets M and Mwill be respectivelyin circuit with motors A F and A F.

hen the main stationary contact-fingers are in position A, all of theresistance Ris in the local circuit, which includes the motors andbrake-magnets, as will be readily seen by referring to Fig. 4. Themomentum of the car acquired from the motors or by reason of adowngrade, or both, will now serve to drive the motors as generators andeach will energize its brake-magnet to a degree determined by the speedof rotation of the armature and the amount of resistance in circuit, thecurrent generated by armature A traversing conductor 0 switch-terminal25, plate 2', terminal brake-magnet M, conductor O, finger 0, strips 01:and 00 and finger G, and the current generated by armature A traversingconductor 0, switch-terminal 71, plate 2', terminal i brake-magnet M andfinger G. From finger G a single path is provided through conductors Oand 0 finger B, strips 00 and finger BF, resistance-sections 'r, 0*, r rand r finger R", conductors O and O to finger Z. From this point twopaths are provided, one being through strips Z) and b finger Zfield-magnet winding F finger 1', strips 5 and b and finger Z toarmature A and the other through strips Z), 19 and b finger Zfield-magnet winding F, finger Z strips 17 and b, and finger Z toarmature A. A further braking effect is produced by moving thecontrollerdrum to bring the main contact-fingers to position B, and thusshort-circuiting the resistance-section r. In position 0resistance-sections 4, r, and r are short-circuited, and in position Eall of the resistance except the portion r is short-circuited. Inposition F none of the resistance is in circuit, this being the maximumor emergency braking position.

In the last-named position the respective paths for thearmature-currents to the finger G are the same as when the controller isin position A, and the single path from this point is through conductorsO and 0 finger B, strips 00 and 00 and finger R and thence as specifiedfor position A.

It will be readily seen that each armature normally supplies current toits own brakemagnet only and that if the conditions are such as to stopthe rotation of either armature the other armature will send ademagnetizing-current through the brake-magnet corresponding to thenon-rotating armature, and thus effect the release of the correspondingtruck-wheels, as has already been pointed out.

I desire it to be understood that my invention is in no wise limited asregards structural details or the relative location of the apparatusemployed.

I claim as my invention- 1. In an electric braking apparatus, aplurality of electric motors arranged in parallel in a local circuit tobe driven as generators, in combination with a plurality ofbrake-magnet-s, one in each branch of such circuit.

2. In an electric braking apparatus, a plurality of electric motorsarranged in parallel in a local circuit to be driven as generators, incombination with a plurality of brake-magnets-one in each branch of suchcircuitand means for automatically cutting both of said magnets out whenthe motors are connected with the main generator.

3. Means for propelling and regulating the speed of vehicles comprisinga plurality of electric motors, means for connecting the same either inseries or in parallel and for varying the resistance of their circuit orcircuits, means for connecting the motors in parallel in a local circuitto be driven as generators by the momentum of the vehicle when thepower-current is shutoff, and a brakemagnet located in each branch ofsaid local circuit.

4. In an electrically-propelled vehicle, the combination with aplurality of motors driven as generators by the momentum of the vehiclewhen the power-current is shut olf, of means for establishing a localcircuit which includes said motors in parallel and a variableresistance, a brake-magnet in each same and means for controlling theirpower and speed, of a plurality of brake-magnets normally out ofcircuit, and means for establishing a local circuit containing avariable resistance and having a plurality of branches each of whichcontains one of the motors and one of the brake-magnets.

In testimony whereof I have hereunto subscribed my name this 20th day ofOctober,

HARRY P. DAVIS.

lVitnesses:

WESLEY G. CARR, IIUBERT O. TENER.

